1. Field of the Invention
This invention relates to a device for measuring parameters of a sled mechanism of an optical disc drive.
2. Description of the Related Art
An optical disc drive for driving an optical disc, such as a compact disc (CD), a CD-ROM or a DVD, includes an optical pickup, referred to below as OP, and an electrical controller for controlling the movement of an objective lens provided in the OP, and is configured for correctly illuminating the laser light emitted from the OP on a track on the optical disc. With such OP, since it is necessary to set mechanical and electro-optical parameters required for stable tracking and track jump under many different conditions, a lot of time and labor are required in newly studying and testing an OP.
It is therefore contemplated to effect computer simulation for an OP to study and test the OP.
For such computer simulation for an OP, parameters of a sled mechanism for causing radial movement of a main body unit of the OP along the radius of the optical disc are required.
Such sled mechanism generally includes a shaft provided radially of the optical disc, a sled motor for driving the OP provided on the shaft and plural gears for transmitting the sled motor rotation to the OP.
However, it is extremely difficult to find a motor constant Km, a viscosity coefficient xcex3 and a Coulomb friction Fc in the sled mechanism, such that these parameters cannot be reflected in the Op simulation. The result is that the Op simulation on the computer cannot be accurate.
It is therefore an object of the present invention to provide a method and apparatus for finding a motor constant Km, a viscosity coefficient xcex3 and a Coulomb friction Fc in a sled mechanism for an optical disc drive.
In one aspect, the present invention provides a parameter measurement device for a sled mechanism of an optical disc drive including means for detecting the back-electromotive force of a sled motor, means for detecting the velocity of the movement velocity of an optical pickup, means for causing movement of the optical pickup and means for calculating a motor constant of the sled mechanism based on the back-electromotive force of the sled motor and on the movement velocity of the optical pickup when the movement means causes the movement of the optical pickup.
In the present parameter measurement device for a sled mechanism, the calculating means finds the motor constant Km based on Eb=KmRmv0, where Eb is the back-electromotive force of the sled motor when the movement means causes the movement of the optical pickup, v0 is the movement velocity of the optical pickup when the movement means causes the movement of the optical pickup and Rm is the resistance of the sled motor.
In another aspect, the present invention provides a parameter measurement device for a sled mechanism of an optical disc drive including means for supplying a rectangular electrical voltage of a voltage magnitude Vm and the time t1 to a sled motor, means for detecting the maximum velocity v0 of the pickup when the rectangular electrical voltage is supplied to the sled motor, the deceleration time t3 of the optical pickup, and the distance x3 traversed by the optical pickup during deceleration thereof, and means for calculating the viscous coefficient and/or the Coulomb coefficient of the sled mechanism of the optical disc drive based on the voltage magnitude Vm, the above time t1, maximum velocity of the pickup v0, deceleration time t3 of the optical pickup, the distance x3 traversed by the optical pickup during deceleration thereof and the motor constant Km.
In the present parameter measurement device for the sled mechanism, xcex3xe2x80x2 and Fxe2x80x2c are found using
Fxe2x80x2c=2xcex3xe2x80x2v0/[exp(xe2x88x922xcex3xe2x80x2t3)xe2x88x921]xe2x80x83xe2x80x83(A)
and
Fxe2x80x2c=(v0xe2x88x922x3xcex3xe2x80x2)/t3xe2x80x83xe2x80x83(B)
while the mass m of the sled mechanism in its entirety is found using
xe2x80x83m=Km/[(v0/t1+Fxe2x80x2c+xcex3xe2x80x2v0)/(Vmxe2x88x92KmRmv0/2)]xe2x80x83xe2x80x83(C)
and the mass m, xcex3xe2x80x2 and Fxe2x80x2c thus found are substituted into
Fc=mFxe2x80x2cxe2x80x83xe2x80x83(D)
and
xcex3=mxcex3xe2x80x2xe2x80x83xe2x80x83(E)
to find the viscosity coefficient xcex3 and the Coulomb friction Fc.
In still another aspect, the present invention provides a method for detecting parameters in a sled mechanism of an optical disc drive, including causing movement of an optical pickup, detecting the back-electromotive force of a sled motor and the movement velocity of the optical pickup on causing movement of the optical pickup, and finding the motor constant of the sled mechanism based on the detected back-electromotive force of the sled motor and the detected movement velocity of the optical pickup.
In the present method, the motor constant Km of a sled motor is found based on Eb=KmRmv0, where Eb is the back-electromotive force of the led motor on causing movement of the optical pickup, v0 is the movement velocity of the optical pickup on causing movement of the optical pickup, and Rm is the resistance of the sled motor.
In yet another aspect, the present invention provides a method for detecting parameters in a sled mechanism of an optical disc drive including the steps of supplying a rectangular electrical voltage of a voltage magnitude Vm and the time t1 to a sled motor, detecting the maximum velocity v0 of the pickup when the rectangular electrical voltage is supplied to the sled motor, the deceleration time t3 of the optical pickup, and the distance x3 traversed by the optical pickup during deceleration thereof; and calculating the viscous coefficient and/or the Coulomb coefficient of the sled mechanism based on the voltage magnitude Vm, the above time t1, maximum velocity of the pickup v0, deceleration time t3 of the optical pickup, the distance x3 traversed by the optical pickup during deceleration thereof and the motor constant Km.
In the present method, xcex3xe2x80x2 and Fxe2x80x2c are found using
Fxe2x80x2c=2xcex3xe2x80x2v0/[exp(xe2x88x922xcex3xe2x80x2t3)xe2x88x921]xe2x80x83xe2x80x83(A)
and
Fxe2x80x2c=(v0xe2x88x922x3xcex3xe2x80x2)/t3xe2x80x83xe2x80x83(B)
while the mass m of the sled mechanism in its entirety is found using
m=Km/[(v0/t1+Fxe2x80x2c+xcex3xe2x80x2v0)/(Vmxe2x88x92KmRmv0/2)]xe2x80x83xe2x80x83(C)
and the mass m, xcex3xe2x80x2 and Fxe2x80x2c thus found are substituted into
Fc=mFxe2x80x2cxe2x80x83xe2x80x83(D)
and
xcex3=mxcex3xe2x80x2xe2x80x83xe2x80x83(E)
to find the viscosity coefficient xcex3 and the Coulomb friction Fc.
With the parameter measurement method and device of the present invention, the motor constant Km, viscous coefficient xcex3 and the Coulomb friction Fc in the sled mechanism of the optical disc drive can be measured accurately.